Devis was born on 10 August 1762, son the artist Arthur Devis 1712-1787.
He entered the Royal Academy Schools and went on to exhibit his work; 10 at the Free Society of Artists; 65 at the Royal Academy and 13 at the British Institution from 1775 to 1821.
The young Devis went as a draughtsman on a voyage to the East Indies in 1782 in the Antelope, but the vessel was wrecked off the Pelew Islands and the crew was stranded for a year on an uninhabited island in 1784. The crew became friendly with the people on the neighbouring islands, took part in the wars of the natives, built a vessel of their own and sailed for Macao, but during the voyage Devis received two wounds from arrows shot from the coast, one in his body, the other on his cheek causing a permanent injury to his jaw.
On arriving in Macao, Devis and the crew travelled on to Canton where they stayed for a year and then Devis left to travel to Bengal where he attracted the attention of Sir William Jones, Lord Cornwallis and General Harris. While in India from 1785 to 1795 he successfully practised portrait and subject paintings.
On his return to England he mainly painted portraits and a few notable history subjects.
In his later years he had financial problems and was helped by John Biddulph of Ledbury.
Devis died of apoplexy in London on 11 February 1822 and is buried in St Giles’s Church yard.